I think the issue then is one of salience (another Grainger criteria). Divorced from any real world consequences the belief can’t be protected either. I think what you’re saying would mean beliefs in face are protected as well. But such beliefs don’t exist detached from racist consequences.
Grainger Criteria 5 (worthy of respect, not incompatible with human dignity or in conflict with fundamental rights of others) was ruled to apply by the court on the Forstater case. For racist beliefs this is clearly not the case.
Both in this case and the recent SC ruling I think we have seen rulings that are defensible in theory only, but that ignore reality and effects of the ruling. That is a worrying development, but only case law will be able to address that.